<!--固定定位-->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>固定定位</title>
    <style>
        .container{
            width: 100%;
            margin: 0 auto;
            text-align: center;
        }
        .fixed_l{
            position: fixed;
            bottom: 50px;
            left: 0;
        }
        .fixed_r{
            position: fixed;
            bottom: 50px;
            right: 0;
        }
    </style>
</head>
<body>
    <div class="container"><img src="pic/box.png" alt="box">
        <div class="fixed_l"><img src="pic/ad-l.png" alt="ad_L"></div>
        <div class="fixed_r"><img src="pic/ad-r.png" alt="ad_R"></div>
    </div>
</body>
</html>